The Limits of The Limits to Growth

Contemplating 1972 predictions of environmental doom, just in time for Earth Day

Forty years ago, The Limits to
Growth, a report to the Club of Rome, was released with great
fanfare at a conference at the Smithsonian Institution. The study
was based on a computer model developed by researchers at the
Massachusetts Institute of Technology (MIT) and designed “to
investigate five major trends of global concern—accelerating
industrial development, rapid population growth, widespread
malnutrition, depletion of nonrenewable resources, and a
deteriorating environment.” The goal was to use the model to
explore the increasingly dire "predicament of mankind." The
researchers modestly acknowledged that their model was “like every
other model, imperfect, oversimplified, and unfinished.”

Yet even with this caveat, the MIT researchers concluded, “If
present growth trends in world population, industrialization,
pollution, food production, and resource depletion continue
unchanged, the limits to growth on this planet will be reached
sometime within the next one hundred years.” With considerable
understatement, they added, “The most probable result will be a
rather sudden and uncontrollable decline in both population and
industrial capacity.” In other words: a massive population crash in
a starving, polluted, depleted world.

The problem, as the MIT researchers saw it, was exponential
growth in all five areas of concern that they investigated. Linear
growth is additive—1, 2, 3, 4, 5—whereas exponential growth
compounds over time—1, 2, 4, 8, 16.

Earlier this month, Smithsonian magazine ran a
short item reporting the findings of a 2008 study [PDF] by
Australian physicist Graham Turner. According to Turner, an
examination of currently available data reveals that that
world economy is right on track to collapse by the middle of this
century. Without taking Turner on directly, let’s look at what
has happened with each global concern highlighted in the original
study since 1972.

Industrial development: World GDP stood in real 2010
dollars at about $19 trillion in 1972 and has tripled to $57
trillion today. Average per capita incomes rose in real dollars
from $5,000 to $8,100 today. Just to explore
how incomes might evolve between 1972 and 2000, the researchers
simply extrapolated the current growth, investment, and population
growth rates to calculate GDP per capita for 10 large countries.
They stressed these were not "predictions" but added that if one
disagreed then one was obligated to specify which factors changed,
when and why. A comparison of their extrapolations with actual GDP
per capita (in 2010 dollars) finds U.S. GDP per capita $56,000
versus actual $44,000; Japan's per capita GDP was projected to be
$120,000 versus actual $46,000; the now defunct USSR would be
$33,000 versus Russia's $2,200; and China's per capita income was
supposed to grow to $500, but was instead $1,200.

Population: The Limits researchers noted,
“Unless there is a sharp rise in mortality, which mankind will
strive mightily to avoid, we can look forward to a world population
of around 7 billion persons in 30 more years.” In addition, they
suggested that in 60 years there would be “four people in the world
for everyone living today.” In fact, average global life expectancy
rose from 60 to nearly 70 years. On the other hand, the
global fertility rate (the average number of children a woman has
during her lifetime) fell from about 6 per woman in 1970 to 2.8
today and continues to fall.

World population stood at 3.8 billion in 1972, which means that
a four-fold increase in 60 years would have yielded a total world
population of 15 billion by 2030. Even the latest U.N. high
fertility population projection foresees about 9 billion by
2030. The U.N.’s low fertility variant yields a maximum world
population of about 8 billion around 2050, falling back to 6
billion by the end of the 21st century. It turns out that the
invisible hand of population control correlates very nicely
with economic freedom.

Food supplies: According to the data from the
Food and Agriculture Organization, global food production has
more than tripled since 1961, while world population has increased
from 3 billion to 7 billion. This means that per capita food has
increased by more than a third. The latest
figures [PDF] from the United Nations show that as world
population increased by a bit over 10 percent between 2000 and
2009, global food production rose by 21 percent.

Arable land was proposed as one possible ultimate limit in the
MIT model. In one generous model run, pollution was controlled and
nonrenewable resources were essentially unlimited. The MIT
researchers assumed that as long as industrial production continued
to rise in the 21st century “the yield from each hectare of
land continues to rise (up to a maximum of seven times the average
yield in 1900) and new land is developed.” Interestingly, since
1900 American corn farmers have
already boosted yields nearly seven-fold from 26 bushels per
acre to 166 bushels per acre. A 2010 article in Philosophical
Transactions of the Royal Society B argued that available
technologies could close the yield gap between first world farmers
and developing country farmers even as the world warms. If this is
done, the article
concluded, “There is a good prospect that crop production will
increase by approximately 50 percent or more by 2050 without extra
land.”

In 1972, the Limits researchers noted that about 1.4
billion hectares of land was being cultivated and projected that if
current crop yields did not improve 3 billion hectares would be
needed by 2000 to feed a projected population of 7 billion. The
Limits analysts did note that if crop yields doubled
(which they did not expect) that land devoted to producing crops
would only increase marginally—which is what actually happened. The
U.N.’s Food and Agricultural Organization reports that since 1960
cropland has expanded from
1.4 billion to 1.5 billion hectares [PDF].

Nonrenewable resources: Probably the most notorious
projections from the MIT computer model involved the future of
nonrenewable resources. The researchers warned: “Given present
resource consumption rates and the projected increase in these
rates, the great majority of currently nonrenewable resources will
be extremely expensive 100 years from now.” To emphasize the point
they pointed out that “those resources with the shortest static
reserve indices have already begun to increase.” For example, they
noted that the price of mercury had increased 500 percent in the
last 20 years and the price of lead was up 300 percent over the
past 30 years. The advent of the “oil crises” of the 1970s lent
some credibility to these projections.

To highlight how dire the situation with nonrenewable resources
was, the MIT researchers calculated how quickly exponential
consumption could deplete known reserves of various minerals and
fossil fuels. Even if global consumption rates didn’t increase at
all, the MIT modelers calculated 40 years ago that known
world copper reserves would be entirely depleted in 36 years, lead
in 26 years, mercury in 13 years, natural gas in 38 years,
petroleum in 31 years, silver in 16 years, tin in 17 years,
tungsten in 40 years, and zinc in 23 years. In other words, most of
these nonrenewable resources would be entirely used up before the
end of the 20th century.

They recognized that it was very likely that undiscovered
reserves would be found and that technological improvements at
extracting resources would occur, so just to be generous they made
the same calculations with known reserves increased five-fold.
Again at exponential consumption rates, they expected that after a
gratuitous five-fold increase in resources there would now be only
15 years of aluminum left, eight years of copper, one year of
mercury, nine years of natural gas, 10 years of petroleum, two
years of silver, 21 years of tin, and 10 years of zinc.

Based on current consumption rates, the U.S. Geological Survey
(USGS) in its 2012
mineral summaries report [PDF] estimates that the world has 130
years of bauxite reserves, which are used to produce aluminum.
Similarly at current consumption rates, known copper reserves will
last 43 years. Known lead reserves will last 18 years, although the
USGS adds that identified lead resources equal 1.5 billion tons and
that would mean a supply lasting somewhat more than 300,000 years.
Mercury reserves are enough to another 48 years, but the USGS
notes, “The declining consumption of mercury, except for
small-scale gold mining, indicates that these resources are
sufficient for another century or more of use.” Current silver,
tin, tungsten, and zinc reserves will respectively last 22, 19, 43,
and 20 years more.

In 1972, the Limits researchers estimated known global
oil reserves at 455 billion barrels. Since then the world has
produced very nearly 1 trillion
barrels [PDF] of oil and current known reserves hover around
1.2
trillion barrels, a 40-year supply at current
consumption rates. With regard to natural gas supplies, the
International Energy Agency last year issued a
report [PDF] asserting, “Conventional recoverable resources are
equivalent to more than 120 years of current global consumption,
while total recoverable resources could sustain today’s production
for over 250 years.”

Why does the horizon of mineral reserves never seem to go out
further than a few decades? Basically because miners and
technologists do not find it worthwhile to find new sources and
develop new production techniques until markets signal that they
are needed. How this process evolves is encapsulated by the USGS
report which notes that in 1970 known world copper reserves stood
at “about 280 million metric tons of copper. Since then, about 400
million metric tons of copper have been produced worldwide, but
world copper reserves in 2011 were estimated to be 690 million
metric tons of copper, more than double those in 1970, despite the
depletion by mining of more than the original estimated
reserves.”

Environment: In most of the Limits model runs,
the ultimate factor that does humanity in is pollution. In their
model pollution directly increases human death rates and also
dramatically reduces food production. In fact, as the world economy
has grown, global average life expectancy has increased from 52
years in 1960 to 70 years now. It must be acknowledged that
globally, pollution
[PDF] from industrial and agricultural production continues to
rise. But the model assumed that pollution would increase at
exponential rates. However, many pollution trends have not
increased exponentially in advanced countries.

Consider that since 1970, the U.S. economy has grown by 200
percent, yet the levels
of air pollutants [PDF] regulated by the federal government
have fallen by nearly 60 percent. For example, in both the U.S. and the
European Union [PDF] sulfur dioxide emissions have dropped by
nearly 70 percent since 1990. Recent data suggests that sulfur
dioxide emissions even from rapidly industrializing China peaked
in 2006 [PDF] and have begun declining. Earlier studies cite
evidence for a pollution turning point income threshold (purchasing
power parity) of
around $10,000 [PDF] for demands to reduce this form of air
pollution.

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My upcoming earth day activities:
1. Burn about 20 lb of propane to brew beers (which will release
CO2 during fermentation)
2. Light a fire to keep warm while brewing outdoors.
3. Use a couple of 500W halogen lamps to light the brewing
area
4. Blast some metal into the forest where I live while brewing.

Ron, I think you need to be writing about food. Maybe a cooking
show, "Cookin' with Ron!" Say, did you hear about the Alan
Greenspan diet? You eat everything in sight, so the poor will
starve to death!

When I am freed from the productive shackles of work, I'm going
to write a book called Limits of Modeling. It will consist
of all the doom and gloom predictions made by experts with computer
models and going back and seeing just how wrong they are.

Can we get some sources for were you get your income data came
from? I did a quick wiki check for GDP per capita, both nominal and
PPP, and IMF, World Bank, or CIA numbers show the US GDP per capita
at $ 44,000.

Come on Ron. 2,4,8,16 is linear (x*c = y (x times c) graphed, x
being the independent variable [in this c (constant) is 2)] on
x&y axis). Exponential is x raised to the power of c = y. If c
is 2 (e.g. squaring), then 1 (1*1),4(2*2), 9 (3*3), 16, etc. The
curve is asymtotic.

"helping those who can't help themselves"; can't wait until the
police are fully involved domestically. We already have the DEA and
prisons helping drug users--if only the could help the fat, the
unemployed, the masses yearning to be politically correct!!!